Tonight, bizarre medical mysteries that stumped even the experts at first. That made people with these strange afflictions won'ter if they were going crazy. That is, until the doctors said they weren't. And we start here tonight, Elizabeth, with one of the strangest afflictions. A newly diagnosed condition that givens a whole new meaning to the term picky eater. Deborah Roberts is there with our cameras as you watch a near breakdown take place over the tiniest bite of food. I'm trying to get it to calm down. Reporter: You're witnessing a grown woman in the midst of a panic attack -- over rice. I don't know. Reporter: Take your time. This is really tough for you, isn't it? Take your time on it. Okay, deep breath. Reporter: You look tormented. Believe it or not, she's never, ever eaten rice. Large order of fries. Reporter: That's because for most of her life, amber Scott has existed mainly on one food -- French fries. Greasy, salty, one of our most guilty culinary pleasures. Though she'll try pizza and bland pasta from time to time, the French fry is about the only thing amber can tolerate. I consider myself a French fry connoisseur. This is how I like them to look. Reporter: If it sounds outrageous to you, amber isn't at all shocked. She knows her eegt habits are bizarre, but can't seem to change them. So how does a divorced mom of a 11-year-old get to this point? Her daughter has a fairly Normal diet. Amber traces it all back to her childhood, sitting at the dinner table facing a plate of peas. And I remember thinking, "I can't do this. I can't do this." Reporter: Not that you won't. Not that I won't. It was almost like a moment of paralysis. It suddenly was not something that was edible to me. Reporter: She might have gone to bed hungry had her mom not caved and let her eat the only thing she could stomach. You guessed it -- French fries. I just had to make French fries three times a day, and she had to eat. If she didn't eat the French fries, she wouldn't eat. Reporter: Today, dinnertime hasn't changed much for amber. On any given day her meal is a plate of fries. Anytime, anywhere. I have Pepsi, diet. Reporter: And only one kind of fry, mind you. Can you make the fries without the peel on them? Reporter: They have to be skinless, hand cut, fried in canola oil. There's something green on that one as well. Reporter: And with nothing more than a hint of salt. Amber drinks just about anything. Milk, soda, red wine. But when it comes to food, proteins, fruits and vejabv vegetables are out of the question. Fish? Chicken? No. None of those ever in my whole life. Reporter: Vegetables. Never had a vegetable. Yeah, I need an order of fries, please. Reporter: It may sound like amber's living a junk food addicts dream, but in reality, she says, it's a living nightmare. Did people think you were strange, not being able to eat the Normal things that people eat? "You can't put this in your mouth and chew it?" No. "Well, why not?" I don't know why. There's no answers right now. None. Reporter: And believe it or not, amber is far from alone. By some estimates, there are thousands of adult picky eaters. People who are tormented by the very thing so many of us find pleasurable -- food. It's a rare eating disorder called avoidant restrictive food intake disorder, or arfid. Doctors like David Katz of Yale university's prevention research center are only now beginning to understand arfid. It's an expression of some extreme sensitivity, at the very least, but may really be almost like a phobia. What keeps you from eating a stick? What is it about looking at a stick that says, "Nope, I can't eat that?" What is it? Reporter: So, some foods just look inedible to you? That's the closest I can get to explaining how it feels. Reporter: It's off-putting for them to even go in a grocery store. Well, because it's traumatizing. Reporter: Nutritional therapist Sondra Kronberg has spent years trying to get tortured eaters like amber to accept different foods. Now amber says, to look at something like strawberries or blueberries -- Oh, I would think those would be a little bit more dangerous, because they look sort of like bugs or animals or some kind -- Reporter: Bugs or animals? Buzz they're blackberries. I have a client who looks at raisins and thinks that they're ants. With mushrooms, people think it's fungus, it's mold. "I don't want to eat it." Reporter: It's an affliction that can wreak havoc on your love life. It would take a long time for me to even build up the nerve to go out with anyone because I thought once they find out they're not going to want to see me again. Reporter: So, it was painful. Sure. Reporter: Amber's former boyfriend, Jim Neil, will never forget their first dinner date. It was pretty much disastrous. Reporter: Disastrous? Yeah. Reporter: In what way? Well, I came to find out that she really could not physically eat anything that was on the menu. Reporter: Could not. Not would not. Reporter: Could not, right. The food was actually repulsive to her. Reporter: Amber says that while she wants to get better, she simply can't. But why can't you, amber? Why can't you just decide and, sort of like any other phobia that people have, just confront this thing and psychologically work your way to do it? I think it goes deeper than that. When you can feel every shard of carrot in your mouth, and you can't get it to go away, that's not psychological anymore, I can feel that. Hey, I'm coming up the ramp. I'll be there in a minute. Reporter: So what happens when she finally agrees to step out of her food comfort zone and try something new? At first, amber refused our request, unless she had the support of Jim, still a close friend. Are you nervous? Are you scared? I'm okay. I came to understand that, yeah, this is something very serious. This is not just, you know, a whim of hers, at all. Reporter: Finally, amber agrees to try something she's never attempted before -- white rice. Rice is not very threatening color-wise. So, what is it going to do? I don't know. Reporter: What happens next is shocking. Even before the rice is served, amber is beginning to sweat. Take your time. When she dissovles into tears, we tell her she can stop. Just give it a shot. That is a lot. Yeah, try just a few. I don't want to get sick. Reporter: Seven agonizing minutes later, amber works up the nerve to consider a few grains of rice. Okay, deep breath. Deep breath. Reporter: You can do it. Be brave. I just don't want to get sick on you guys. Reporter: No, you won't, you won't get sick. Her panic barely contained. You okay? Amber struggles to hold back her gag reflex. You did it. You okay? Not going to get sick are you? It won't go down. Okay, okay. Reporter: It won't go down? Relax with it. Reporter: Good for you. There you go. Reporter: You tried it. After enduring our experiment, amber declares she won't be trying a new food any time soon. How is it you can go through life only eating carbs and no vegetable and no protein? Are you healthy? I'm very healthy. I've had test after test done, and I'm very healthy, there is nothing wrong with me. Reporter: Amber gaveus permission to check with her doctor, who told us the results of her last physical were Normal. But her eating habits have prompted scorn and anger from others who see her simply as stubborn. I've heard it all, I mean, amber's now in law school and is even recording a podcast. It's a very old fashioned kind of mentality to tell your children you'll eat what I made or you'll starve. Reporter: -- To help others make sense of a disorder very few of us understand. Now I know that I didn't do something to myself and that is a big first step. It gives you hope.

This transcript has been automatically generated and may not be 100% accurate.

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